Today, following a two-year investigation, the Health and Safety Executive (HSE) confirmed it will be taking no further enforcement action.

Following the incident, it issued Beamish with an improvement notice which required staff to assess the risks to people using the steam engines and ensure those risks were communicated to anyone using the engines.

Chris Gillies, HSE principal inspector who led the investigation, said that HSE was satisfied that the risks from the use of steam traction engines at Beamish were now properly controlled.

Durham Police/PA Wire

Seven-year-old Karl Doran, of Darlington, who died at Beamish Museum

He said: “HSE propose to work with Beamish Museum and similar organisations to ensure other operators of steam traction engines are aware of the risks and the measures necessary to control those risks, particularly when children are being carried.

“It would not be in the public interest to take further enforcement action against the museum.”

An inquest, held in December 2013, recorded a verdict of accidental death.

Detective chief inspector Victoria Fuller, from Durham Police, showed the jury at Crook Civic Centre photos and video of Karl on the day he died that were sent in by the public after an appeal in the wake of the tragedy.

In them the youngster – dressed in an old-fashioned outift of black trousers, a white shirt, dark waistcoat, and flat cap – could be seen both alongside his father in the cab, standing on the vehicle’s tow bar, and sitting on the A-frame between the road roller and the large steel-wheeled “Tarmac Limited” trailer it was pulling.

Minutes before his death, Philip had told Karl to move to the back off the engine after he sat dragging his feet on the ground as the roller trundled along at less than seven miles per hour.

After the incident Mr Doran flagged down a passing tram and medically trained museum visitors rushed to help, but there was nothing they could do.

Director of the museum Richard Evans has said the safety of visitors is their top priority.